Combustion-powered, fastener-driving tools of a type exemplified in Nikolich U.S. Pat. No. Re. 32,452 and Nikolich U.S. Pat. No. 5,197,646 are available commercially from ITW Paslode (a unit of Illinois Tool Works Inc.) of Vernon Hills, Ill., and are used widely in building construction.
Typically, such a tool comprises a combustion chamber, a piston chamber communicating with the combustion chamber, a driving piston movable within the piston chamber over a stroke between an initial position and a terminal position, and a driving blade mounted to the driving piston so as to be conjointly movable with the driving piston. Combustion in the combustion chamber imparts energy to the driving piston and the driving blade so as to drive the driving piston and the driving blade over a stroke from an initial position toward a terminal position with the driving blade preceding the driving piston. Typically, the driving blade is guided by passing through or between guides, over the entire stroke of the driving blade.
Generally, such a tool also comprises means for sensing when the tool is pressed against a workpiece, for enabling the tool when the tool is pressed against a workpiece, and for disabling the tool when the tool is not pressed against a workpiece, together with means including a trigger for initiating combustion in the combustion chamber when the tool is enabled and the trigger is actuated.
It has been found that such tools known heretofore transfer less than one half of the maximum, transferable energy to a fastener engaged by the driving blade as the driving piston and the driving blade approach the terminal position. It would be highly desirable to provide such a tool that could transfer substantially more of the maximum, transferable energy to a fastener engaged by the driving blade as the driving piston and the driving blade approach the terminal position.